Authz restrict

[Max rz]

Hi,
I have authz file like this

  [groups]
admin = (some admins)
 users = (some users) 
 [/]
* = r
@users = rw
@admin = rw
 [/directory]
* = r
@users = rw
@admin = rw

how do I add a special user, that can access only a subdirectory in directory?
I tried something like
 [/directory/subdirectory]
* = r
specialuser = rw
@users = rw
@admin = rw
Or like this


 [/]
* = r
@users = rw
@admin = rw
specialuser = 
 [/directory]
* = r
@users = rw
@admin = rw
specialuser = 
 [/directory/subdirectory]
* = r
specialuser = rw
@users = rw
@admin = rw
But it didnt work. specialuser still can export and change files in directory